The Shear Strength Characteristics of Red Clay Kai

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The Shear Strength Characteristics of Red Clay Kai
5th International Conference on Advanced Design and Manufacturing Engineering (ICADME 2015)
The Shear Strength Characteristics of Red Clay
Kai sheng Chen1, a *,Zhen Lu2,b
1
School of Civil Engineering, Guizhou University Guizhou Guiyang China
2
School of Civil Engineering, Guizhou University Guizhou Guiyang China
a
[email protected], [email protected]
*[email protected]
Keywords: red clay;direct shear test;shear strength characteristics
Abstract.The paper is aimed at the phenomenon of red clay subgrade disease,taking the subgrade
filling from the Yuqing-Kaili Expressway as the research object,the soil mechanics as the theoretical
foundation,the testing technology of geotechnical engineering as the method,resrearched the
change regulation of the strength characteristics of red clay。The research findings not only has the
important academic value for improving the evaluation system of red clay road,but also has some
engineering practical significance to the highway construction in the red clay area,Besides this,it
can provide technology reference for other industries.
Foreword
The red clay has high moisture content, high plasticity, high void ratio and other special
engineering properties,and there is more rain in South China,during the drying and wetting cycle,
the long-term strength and stability of red clay subgrade descend,caused the subgrade to have some
disease,as subgrade settlement,pavement crack,transverse crack,shoulder collapse,slope
sliding,collapse and landslide.So it is has great important meaning to research the strength
characteristics of red clay.
Basic physical properties of Red clay
Field Sampling.The red clay used in this experiment is from Yuq ing-Kaili Expressway。Thsee red
clay's colors are brown red, brown red and brown yellow.The soil taking form subgrade is a little
dry,and uniform,these soil's structure is compact;The soil taking form cutting slope is a little damp
and loose,the amount of pieces of leaves and plant root tip in these soil is very little.Form the
analysis of the particle compositicle,finding the soil sample is mianly clay.The natural water content
is high, the viscosity property is strong,the void ratio is big,the liquid limit is a little higher and in
the soft plastic state.
Basic physical properties of Red clay
JTG E40-2007
Optimu m moisture
content(%)
37.2
Table1 Basic physical properties of red clay
>0.075mm(%)
0.074~0.002mm(%)
<0.002mm (%)
17.25
71.41
11.34
Plastic
Liquid
Plasticity
Maximu m dry unit
Proportion
limit(%)
limit (%)
Index
weight(g/cm3)
38
59
21
2.720
1.46
© 2015. The authors - Published by Atlantis Press
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Testing Program
Sample Preparation
Moisture content/%
30
34
37.2
40
44
75
75
75
75
75
Table2 Samp le preparation
Degree of Co mpaction/%
85
90
85
90
85
90
85
90
85
90
96
96
96
96
96
Test Method.When the soil sample prepared,do the unconsolidated-undrained triaxial shear test,
set the vertical stress as 100kpa , 200kpa , 300kpa and 400kpa , and the shear rate is
0.8mm/min.When the shear displacement value reach 4mm,press the pause button and write down
the damage value;When the process of shear without peak value,should shear until the displacement
value reach 6mm.And taking the shear stress as the longitudinal coordinate,the shear displacement
as the horizontal coordinate,then draw the shear stress-displacement curve,at last calculate cohesion
value and angle of internal friction.
Experime nt Result
Shear stress-displacement curve
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Fig.1
Shear stress-displacement curve
Form these curves,we can find Shear stress-displacement curve is begin steep,when the strain
reached a certain value the curve is begin smooth,there is no peak value,it's appear as weakly
hardening type.
Shear strength index-Moisture conten curve,shear strength index-Degree of compaction curve
(1)Shear Strength Index
Moisture
conten/%
30
34
37.2
40
44
75
38.23
26.44
23.71
8.61
17.42
Table3 Cohesion value c(kpa)
Degree of Co mpaction/%
85
90
52.73
56.24
47.24
52.23
45.26
50.24
42.03
47.26
37.02
41.12
Table4 The angle of
Moisture
conten/%
30
34
37.2
40
44
75
14.47
12.73
7.79
8.72
11.24
internal friction
Degree of Co mpaction/%
85
90
17.36
19.35
16.02
18.21
14.02
17.23
11.32
13.02
9.81
10.89
96
64.48
60.25
55.21
52.36
47.24
96
21.23
19.75
17.53
15.02
11.89
(2)The relationship between shear strength index with Moisture conten,the relationship between
shear strength index with Degree of compactness
Fig.2 Cohesion value -Moisture content
curve
Fig.3 Cohesion value -Degree of
co mpactness curve
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Fig.4 The angle of internal frict ionMoisture content curve
Fig.5 The angle of internal frictionDegree of co mpactness curve
Conclusion
(1)The cohesion value c decreases monotonically with the increase of moisture conten , and
increases monotonically with the increase of the degree of compactness k.
(2)The angle of internal friction decreases monotonically with the increase of the moisture
content , and increases monotonically with the increase of the degree of compactness k..
(3)The amplitude of cohesion value C varies with the change of moisture conten
of compactness K than that of angle of internal friction.
and degree
Acknowledge ments
This work was financially supported by National Natural Science Foundation of China
(Approval number:51368010)and Guizhou science and Technology Department — Guizhou
University Foundation(Qiankehe Lh zi[2014]).
References
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Stress Paths[J]. Journal of Rock Mechanics and Geotechnical Engineering , 2004 ,
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[2]Zhizheng Xiao,Baoshen Liu.Experimental study on the Mechanical Strength of Residual
Laterite[J].Journal of Underground Space and Engineering,2005,l(7):990-993
[3]Qingtao Bi,Guoping Jiang,Shuyun Ding.Water Content Influence On The Shearing Strength
On Red Clay[J].Journal of Earth and Environment,2005,33(3):144-147
[4]Jingyang Li.Mechanical Strength of Residual Laterite in Guizhou[J].Journal of Guizhou
University of Technology,1997,26(2):73-78
[5]Chun LIu,XuChun Wu.Research of the strength characteristics of unsaturated red clay based on
general tri-axial test.[J].Journal of Building Science Research of Sichuan.2003,29(2):65-73.
[6]Kaisheng Chen , Yuan Yin.Experimental Research of Strength Index of Red Clay for
Guiyang-Qingzhen Expressway [J]. Journal of Highway and Transportation Research and
Development,2011,28(3) :61-66
[7]Heping Yang,Rui Zhang,Jianlong Zheng. Variation of deformation and strength ofexpansive soil
during cyclic wetting and drying under loading condition[J].Geotechnical Engineering,2006,
28(11):1936-1941
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